Solid-state image pickup apparatus and image pickup system

ABSTRACT

An apparatus according to the present invention in which a first substrate including a photoelectric conversion element and a gate electrode of a transistor, and a second substrate including a peripheral circuit portion are placed upon each other. The first substrate does not include a high-melting-metal compound layer, and the second substrate includes a high-melting-metal compound layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.13/898,264, filed May 20, 2013, which is a Continuation of U.S.application Ser. No. 12/975,088, filed Dec. 21, 2010, now becomes U.S.Pat. No. 8,466,403 issued Jun. 18, 2013, which claims priority fromInternational Application No. PCT/JP2009/071703, filed Dec. 26, 2009,which are hereby incorporated by reference herein in their entireties.

TECHNICAL FIELD

The present invention relates to a backside-illumination solid-stateimage pickup apparatus.

BACKGROUND ART

Recent higher-speed solid-state image pickup apparatuses have caused theproposal of a structure in which a semiconductor compound layer isprovided at a transistor.

Japanese Patent Laid-Open No. 2001-111022 discusses a solid-state imagepickup apparatus in which a high-melting-metal semiconductor compoundlayer is not provided on a photodetector of a photoelectric convertingsection, and a high-melting-metal semiconductor compound layer isprovided at a peripheral circuit portion.

Japanese Patent Laid-Open No. 2009-170448 discusses abackside-illumination solid-state image pickup apparatus in which, inorder to increase sensitivity of a photoelectric conversion element, asubstrate including a pixel portion provided with the photoelectricconversion element and a signal-readout circuit, and a substrateincluding a peripheral circuit for processing a read-out signal bydriving the circuit of the pixel portion are adhered to each other.

In the structure in which a high-melting-metal semiconductor compoundlayer is provided at the peripheral circuit portion in Japanese PatentLaid-Open No. 2001-111022, since a high-melting metal is provided on thesame substrate, the high-melting metal may be diffused to thephotoelectric conversion element. Even if a surface of the photoelectricconversion element is protected by an insulating film, the high-meltingmetal may become diffused in the insulating film since, for example, astep of forming the high-melting metal on the insulating film exists. Inaddition, for example, a white defect may occur in an image due toleakage current generated as a result of contamination of thephotoelectric conversion element by the high-melting metal. Further, inorder to form the structure discussed in Japanese Patent Laid-Open No.2001-111022, it is necessary to determine where to form the high-meltingmetal semiconductor compound layer on the same substrate, therebycomplicating the process.

Accordingly, it is an object of the present invention to provide, byusing a simple structure, a solid-state image pickup apparatus in whicha high-melting-metal compound layer is disposed at a peripheral circuitportion while a reduction in the characteristics of a photoelectricconversion element, which causes, for example, a white defect to beproduced, is suppressed.

SUMMARY OF INVENTION

The present invention provides an apparatus in which a first substrateand a second substrate are placed upon each other, the first substratebeing where a photoelectric conversion element and a gate electrode fortransferring an electric charge from the photoelectric conversionelement are disposed, the second substrate being where a peripheralcircuit portion for reading out a signal based on the electric chargegenerated at the photoelectric conversion element is disposed, whereinthe second substrate is provided with a high-melting-metal compoundlayer, and the first substrate is not provided with a high-melting-metalcompound layer.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a solid-state image pickup apparatus usedto describe a first embodiment.

FIG. 2 is a sectional view of a solid-state image pickup apparatus usedto describe a second embodiment.

FIG. 3 is a sectional view of a solid-state image pickup apparatus usedto describe a third embodiment.

FIGS. 4A and 4B show a method of manufacturing the solid-state imagepickup apparatus according to the third embodiment.

FIGS. 5A and 5B show the method of manufacturing the solid-state imagepickup apparatus according to the third embodiment.

FIG. 6 is a sectional view of a solid-state image pickup apparatus usedto describe a fifth embodiment.

FIGS. 7A and 7B show a method of manufacturing a solid-state imagepickup apparatus according to a fourth embodiment.

FIGS. 8A and 8B show the method of manufacturing the solid-state imagepickup apparatus according to the fourth embodiment.

FIG. 9 shows the method of manufacturing the solid-state image pickupapparatus according to the fourth embodiment.

FIGS. 10A to 10C are sectional views of solid-state image pickupapparatuses used to describe the fifth embodiment.

FIGS. 11A to 11C are sectional views of solid-state image pickupapparatuses used to describe a sixth embodiment.

FIG. 12 is an exemplary circuit of the solid-state image pickupapparatus according to the present invention.

FIG. 13 is a block diagram illustrating an image pickup system accordingto a seventh embodiment.

DESCRIPTION OF EMBODIMENTS

A solid-state image pickup apparatus according to the present inventionis formed by placing a first substrate and a second substrate upon eachother, with the first substrate being provided with a photoelectricconversion element and a gate electrode for transfer and the secondsubstrate being provided with a peripheral circuit portion. Ahigh-melting-metal compound layer is not provided at the firstsubstrate, whereas a high-melting-metal compound layer is provided atthe second substrate. By such a structure, it becomes easier todetermine where to form the compound layer, and it becomes possible fora transistor at the peripheral circuit portion to operate at a higherspeed, and a signal readout operation to be performed at a high speedwhile suppressing a reduction in the characteristics of thephotoelectric conversion element.

The present invention will hereunder be described in detail withreference to the drawings.

First Embodiment

A first embodiment of the present invention will be described withreference to FIGS. 1 and 12.

First, an exemplary circuit of a solid-state image pickup apparatusaccording to the first embodiment will be described with reference toFIG. 12. A solid-state image pickup apparatus 300 shown in FIG. 12includes a pixel portion 301, in which a plurality of photoelectricconversion elements are arranged, and a peripheral circuit portion 302,provided with a control circuit for performing a driving operation forreading out a signal from the pixel portion 301 and with a signalprocessing circuit that processes the readout signal.

In the pixel portion 301, a plurality of photoelectric conversionelements 303, transfer transistors 304, amplification transistors 306,and reset transistors 307 are disposed. A structure including at leastone photoelectric conversion element 303 is defined as a pixel. Onepixel in the embodiment includes the photoelectric conversion element303, the transfer transistor 304, the amplification transistor 306, andthe reset transistor 307. A source of the transfer transistor 304 isconnected to the photoelectric conversion element 303, and a drainregion of the transfer transistor 304 is connected to a gate electrodeof the amplification transistor 306. A node corresponding to the gateelectrode of the amplification transistor 306 is defined as a node 305.The reset transistor is connected to the node 305, and an electricpotential of the node 305 is set to any electric potential (for example,a reset electric potential). Here, the amplification transistor 306 is aportion of a source follower circuit, and a signal corresponding to theelectric potential of the node 305 is output to a signal line RL.

The peripheral circuit portion 302 includes a vertical scanning circuitVSR for supplying a control signal to the gate electrode of thetransistor of the pixel portion 301. The peripheral circuit portion 302includes a readout circuit RC holding a signal output from the pixelportion 301 and including a signal processing circuit for amplification,addition, AD conversion, etc. In addition, the peripheral circuitportion 302 includes a horizontal scanning circuit HSR of a controlcircuit that controls timing with which signals from the readout circuitRC are successively output.

Here, the solid-state image pickup apparatus 300 according to the firstembodiment is formed by placing two chips upon each other. The two chipsare a first chip 308 including a photoelectric conversion element 303and a transfer transistor 304 of the pixel portion 301, and a secondchip 309 including an amplification transistor 306 and a resettransistor 307 of the pixel portion 301 and the peripheral circuitportion 302. In such a structure, a control signal is supplied to thegate electrode of the transfer transistor 304 of the first chip 308 fromthe peripheral circuit portion 302 of the second chip 309 through aconnection portion 310. A signal generated at the photoelectricconversion element 303 of the first chip 308 is read out to the node 305through a connection portion 311 connected to the drain region of thetransfer transistor 304. By providing the reset transistor 307 and theamplification transistor 306 at a different chip in this way, it ispossible to increase the area of the photoelectric conversion element303, and to increase sensitivity. If the area of the photoelectricconversion element 303 is the same, many photoelectric conversionelements 303 can be provided, thereby making it possible to increase thenumber of pixels.

Next, a solid-state image pickup apparatus according to an embodimentwill be described with reference to FIG. 1. FIG. 1 is a sectional viewof a solid-state image pickup apparatus 100 corresponding to thesolid-state image pickup apparatus 300 shown in FIG. 12. FIG. 1 is asectional view that is in correspondence with the photoelectricconversion elements 303, the transfer transistors 304, and theamplification transistors 306 shown in FIG. 12. The other portions arenot described. FIG. 1 shows a structure for two pixels.

FIG. 1 shows a first chip 101, a second chip 102, and a bonding surface103 of the first chip and the second chip. The first chip 101corresponds to the first chip 308 shown in FIG. 12, and the second chip102 corresponds to the second chip 309 shown in FIG. 12.

The first chip 101 has a first substrate 104. A surface of the firstsubstrate 104 where a transistor is formed is a principal surface 105,and a surface thereof opposite thereto is a back surface 106. A portionconstituting the photoelectric conversion element 303 and the transfertransistor 304 shown in FIG. 12 is disposed at the first substrate 104.A multilayer wiring structure 107, including a first wiring layer 122and a second wiring layer 123, which, for example, have wires whose maincomponent is aluminum (aluminum wires), is provided on an upper portionat a principal-surface-105-side of the first substrate 104 of the firstchip 101. Here, a plurality of interlayer insulating films of themultilayer wiring structure 107 are described as an integral insulatingfilm.

The second chip 102 has a second substrate 108. A surface of the secondsubstrate 108 where a transistor is formed is a principal surface 109,and a surface thereof opposite thereto is a back surface 110. Amultilayer wiring structure 111, including a first wiring layer 128 anda second wiring layer 129, which, for example, have aluminum wires, isprovided on an upper portion of the principal surface 109 of the secondsubstrate 108. Even here, a plurality of interlayer insulating films ofthe multilayer wiring structure 111 are described as an integralinsulating film. An amplification transistor 306 shown in FIG. 12 isdisposed at the second substrate 108. In the description, in each chip,a direction from the principal surface of the substrate to the backsurface is defined as a downward direction or a deep direction, and adirection from the back surface to the principal surface is defined asan upward direction or a shallow direction.

Here, in the solid-state image pickup apparatus according to theembodiment, the substrate principal surface 105 of the first chip 101and the substrate principal surface 109 of the second chip 102 areplaced upon each other so as to face each other. In FIG. 1, in astructure of a connection portion of the first chip 101 and the secondchip 102, a connection between a floating diffusion region (FD region)113 of the first chip 101 and the gate electrode 126 of an amplificationtransistor 126 of the second chip 102 is only shown. More specifically,the FD region 113 of the first chip 101 is connected to the gateelectrode 126 of the amplification transistor through the multilayerwiring structure 107, a connection portion 311, and the multilayerwiring structure 111. The connection portion 310 shown in FIG. 12 thatsupplies a control signal to the gate electrode 114 of the transfertransistor is not shown in FIG. 1. The solid-state image pickupapparatus according to the embodiment is a backside-illuminationsolid-state image pickup apparatus upon which light is incident from theback surface 106 of the first substrate 104.

Each chip will be described in detail. First, a well 115, an N-typecharge storage region 112 constituting the photoelectric conversionelement, and the gate electrode 114 of the transfer transistor aredisposed at the first substrate 104 of the first chip 101. Further, aP-type surface protection layer constituting the photoelectricconversion element is disposed on the upper portion of the chargestorage region 112. Further, a P-type semiconductor region 116, anelement isolation region 117, and the drain region 113 of the transfertransistor are disposed at the first substrate 104. The well 115 is asemiconductor region where the transistor and the photoelectricconversion element are disposed, and, here, may be either a N type or aP type. The P-type semiconductor region 116 can suppress dark currentgenerated at an interface between a silicon oxide film and silicon ofthe back surface 106 of the first substrate 104, and can even functionas a portion of the photoelectric conversion element. The charge storageregion 112 stores electric charge (electrons) generated at thephotoelectric conversion element, and has a P-type surface protectivelayer at a gate-electrode-side of the transfer transistor in FIG. 1. Theelement isolation region 117 is formed of a P-type semiconductor region,and, although not shown, may have an element isolation structureincluding an insulating film such as a LOCOS isolation layer or a STIisolation layer. The drain region 113 of the transfer transistor is anFD region, and constitutes the node 305 shown in FIG. 12. Aback-surface-106-side of the first substrate 104 of the first chip 101is provided with an antireflection film 118, a light-shielding film 119,a color filter layer 120 including a planarizing layer, and a microlens121.

Next, a well 124, a source region and drain region 125, and the gateelectrode 126 of the amplification transistor 306 in FIG. 12, and anelement isolation region 127 are disposed at the second substrate 108 ofthe second chip 102. The well 124 is a P-type semiconductor region.Here, the source region and drain region 125 of the transistor (theamplification transistor 306 shown in FIG. 12), disposed at the secondchip 102 of the solid-state image pickup apparatus according to theembodiment, include a high-melting-metal compound layer 130. A regionconstituting the peripheral circuit portion 302 shown in FIG. 12,disposed at the second chip 102, is also similarly provided with atransistor including a high-melting-metal compound layer (not shown).The high-melting-metal compound layer is, for example, silicide usingcobalt or titanium, which is a high-melting metal, when silicon is usedin the semiconductor substrate.

A high-melting-metal compound layer is not formed at, for example, thetransistor of the first substrate 104. The insulating film of amultilayer wiring structure is disposed at the upper portion of theprincipal surface 105 of the first substrate 104. Accordingly, ahigh-melting-metal compound layer is not formed at the first substrate104 and the transistor of the peripheral circuit portion disposed at thesecond substrate has a high-melting-metal compound layer, so that it ispossible to increase the speed of operation of the transistor whilereducing noise. In addition, by providing the transistor including sucha high-melting-metal compound layer only at the second chip 102, it ispossible to reduce mixing of the high-melting metal into thephotoelectric conversion element, and to reduce noise generated by themixture of the high-melting metal. Since it is not necessary to form aregion where a high-melting-metal compound layer is to be provided and aregion where a high-melting-metal compound layer is not to be providedon the same substrate, it is not necessary to form, for example, aprotective film to prevent the formation of a high-melting-metalcompound layer, that is, it is possible for each substrate to have asimple structure and to manufacture it using a simple step.

In the embodiment, in addition to the photoelectric conversion element,the FD region is formed at the first substrate 104. This is because, ifa high-melting-metal compound layer is provided at the photoelectricconversion element and the semiconductor region constituting the FDregion which hold signal charges, noise generated when a high-meltingmetal is mixed into the semiconductor region mixes in the signalelectric charges. If the amplification transistor is disposed at thefirst substrate, a high-melting-metal compound layer is not formed atthe amplification transistor.

Although, in the embodiment, each wiring layer is formed of aluminumwires, each wiring layer may be formed of wires whose main component iscopper (copper wires). A diffusion prevention film, which preventsdiffusion of copper, may also be provided at upper portions of thecopper wires, and the diffusion prevention film, which preventsdiffusion of copper, may be subjected to patterning.

Second Embodiment

A solid-state image pickup apparatus according to this embodiment willbe described with reference to FIG. 2. The solid-state image pickupapparatus according to the embodiment is similar to the solid-stateimage pickup apparatus according to the first embodiment in that itscircuits are equivalent to those shown in FIG. 12, and differs therefromin its chip stacking structure. A description of the circuits willhereunder be omitted. The structure shown in FIG. 2 will hereunder bedescribed.

FIG. 2 is a sectional view of a solid-state image pickup apparatus 200corresponding to the circuits shown in FIG. 12. FIG. 2 is a sectionalview for two pixels in correspondence with the photoelectric conversionelements 303, the transfer transistors 304, and the amplificationtransistors 306 shown in FIG. 12, and does not show the other portions.

FIG. 2 shows a first chip 201, a second chip 202, and a bonding surface203 of the first chip and the second chip. The first chip 201corresponds to the first chip 308 shown in FIG. 12, and the second chip202 corresponds to the second chip 309 shown in FIG. 12.

The first chip 201 has a first substrate 204. A surface of the firstsubstrate 204 where a transistor is formed is a principal surface 205,and a surface thereof opposite thereto is a back surface 206. A portionconstituting the photoelectric conversion element 303 and the transfertransistor 304 shown in FIG. 12 is disposed at the first substrate 204.A multilayer wiring structure 207, including a first wiring layer 222and a second wiring layer 223, which, for example, have aluminum wires,is provided on an upper portion at the principal surface 205 of thefirst substrate 204. Here, a plurality of interlayer insulating films ofthe multilayer wiring structure 207 are described as an integralinsulating film.

The second chip 202 has a second substrate 208. A surface of the secondsubstrate 208 where a transistor is formed is a principal surface 209,and a surface thereof opposite thereto is a back surface 210. Amultilayer wiring structure 211, including a first wiring layer 228 anda second wiring layer 229, which, for example, have aluminum wires, isprovided on an upper portion of the principal surface 209 of the secondsubstrate 208. Even here, a plurality of interlayer insulating films ofthe multilayer wiring structure 211 are described as an integralinsulating film. An amplification transistor 306 shown in FIG. 12 isdisposed at the second substrate 208.

Here, in the solid-state image pickup apparatus according to theembodiment, the principal surface 205 of the first substrate 204 and theback surface 210 of the second substrate 208 are placed upon each otherso as to face each other. In FIG. 2, in a structure of a connectionportion of the first chip 201 and the second chip 202, a connectionbetween an FD region 213 of the first chip 201 and a gate electrode 226of an amplification transistor of the second chip 202 is only shown.More specifically, the FD region 213 of the first chip 201 is connectedto the gate electrode 226 of the amplification transistor through themultilayer wiring structure 207, a connection portion 311, and themultilayer wiring structure 211. Here, a through electrode 235constituting a portion of the connection portion 311 and penetrating thesecond substrate 208 is disposed. By the through electrode, the FDregion 213 and the gate electrode 226 of the amplification transistorare connected to each other. The connection portion 310 shown in FIG. 12that supplies a control signal to the gate electrode 214 of the transfertransistor is not shown in FIG. 2. The solid-state image pickupapparatus according to the embodiment is a backside-illuminationsolid-state image pickup apparatus upon which light is incident from theback surface 206 of the first substrate 204.

Next, each chip will be described in detail. A well 215, an N-typecharge storage region 212, constituting the photoelectric conversionelement, and the gate electrode 214 of the transfer transistor aredisposed at the first substrate 204 of the first chip 201. Further, aP-type semiconductor region 216, an element isolation region 217, andthe drain region 213 of the transfer transistor are disposed at thefirst substrate 204. A back-surface-206-side of the first substrate 204of the first chip 201 is provided with an antireflection film 218, alight-shielding film 219, a color filter layer 220 including aplanarizing layer, and a microlens 121. Next, a well 224, a sourceregion and drain region 225, and the gate electrode 226 of theamplification transistor 306 in FIG. 12, and an element isolation region227 are disposed at the second substrate 208 of the second chip 202. Inaddition, the first wiring layer 228 and the second wiring layer 229 areprovided at the upper portion of the second substrate 208, and aninsulating layer 234 is provided at a deepest portion of the secondsubstrate 208. The structures of the first chip 201 and the second chip202 are similar to those of the first embodiment, so that they will notbe described below.

In the second embodiment, an adhesive layer 232 and a supporting base233 are further provided at the upper portion of the second chip 202.The insulating layer, the adhesive layer 232, and the supporting base233 in the second embodiment will be described later.

Here, the source region and drain region 225 and the gate electrode 226of the transistor (the amplification transistor 306 shown in FIG. 12)disposed at the second chip 202 of the solid-state image pickupapparatus according to the embodiment have high-melting-metal compoundlayers 230. A region constituting the peripheral circuit portion 302shown in FIG. 12, disposed at the second chip 202, is also similarlyprovided with a transistor including a high-melting-metal compound layer(not shown). The high-melting-metal compound layer is, for example,silicide using cobalt or titanium, which is a high-melting metal, whensilicon is used in the semiconductor substrate. The transistor of, forexample, the peripheral circuit portion disposed at the second substratehas a high-melting-metal compound layer, so that it is possible toincrease the speed of operation of the transistor. In addition, byproviding the transistor including such a high-melting-metal compoundlayer only at the second chip 202, it is possible to reduce mixing ofthe high-melting metal into the photoelectric conversion element, whilesuppressing a reduction in the characteristics of the photoelectricconversion element of the first chip 201. Since it is not necessary toform a region where a high-melting-metal compound layer is to beprovided and a region where a high-melting-metal compound layer is notto be provided on the same substrate, it is not necessary to form, forexample, a protective film to prevent the formation of ahigh-melting-metal compound layer, that is, it is possible for eachsubstrate to have a simple structure and to manufacture it using asimple step.

Third Embodiment

A solid-state image pickup apparatus according to this embodiment willbe described with reference to FIG. 3. The solid-state image pickupapparatus according to the embodiment corresponds to the solid-stateimage pickup apparatus 100 according to the first embodiment, anddiffers therefrom in that it includes a diffusion prevention film. Thestructure shown in FIG. 3 will hereunder be described. The structuralfeatures that are equivalent to those of the first embodiment will notbe described.

In a solid-state image pickup apparatus 400 shown in FIG. 3, a diffusionprevention film 131 is disposed between a first chip 101 and a secondchip 102. By providing such a diffusion prevention film 131, it ispossible to suppress diffusion of a high-melting metal of ahigh-melting-metal compound layer disposed at the second chip intomultilayer wiring structures 111 and 107 and mixture of the high-meltingmetal into a semiconductor region constituting an FD region and aphotoelectric conversion element of the first chip. Therefore, it ispossible to further suppress generation of leakage current causing awhite defect (of an image) or a dark current to be produced when thehigh-melting metal is mixed into the semiconductor region.

A method of producing the solid-state image pickup apparatus 400 shownin FIG. 3 will be described with reference to FIGS. 4A and 4B and 5A and5B. First, in FIG. 4A, a photo-diode formation member (hereunderreferred to as “PD formation member”) 401, which becomes a firstsubstrate 104 shown in FIG. 3, and a circuit formation member 402, whichbecomes a second substrate 108 shown in FIG. 3, are provided. Thesemembers are, for example, silicon semiconductor substrates, and may beof any conductivity type. The PD formation member 401 includes a p-typesemiconductor region 116 and an insulating layer 403. The PD formationmember 401 uses an SOI substrate, and the p-type semiconductor region116 may be formed by epitaxial growth or ion implantation.

Next, as shown in FIG. 4B, elements such as a gate electrode 114 of atransfer transistor and a charge storage region 112 are formed at the PDformation member 401. The multilayer wiring structure 107 is formed onthe upper portion of the PD formation member 401. The multilayer wiringstructure 107 has a first wiring layer 122 and a second wiring layer123. The first wiring layer 122 and the second wiring layer 123 includea plurality of wires. The wires in the embodiment are aluminum wires.The multilayer wiring structure 107 has an interlayer insulating filmfor insulating the wires from each other. For example, the interlayerinsulating film is disposed between the first wiring layer 122 and thegate electrode of the transfer transistor, and between the first wiringlayer 122 and the second wiring layer 123. For forming the multilayerwiring structure 107, a general semiconductor process may be used.Finally, an interlayer insulating film covering the second wiring layeris formed, and portions thereof are removed so that some wires of thesecond wiring layer 123 are exposed. The exposed second wiring layer 123constitute a connection portion 311. A surface of the PD formationmember 401 where the gate electrode of the transfer transistor is formedbecomes a principal surface 105 of the first substrate described later.

In FIG. 4B, a well 124 and a peripheral circuit portion including atransistor such as an amplification transistor 306 are formed at thecircuit formation member 402. Then, a high-melting metal is deposited onpredetermined positions, such as a source region, a drain region 125,and a gate electrode 126 of the transistor, and heat treatment isperformed, thereby forming a high-melting-metal compound layer 130.Thereafter, a multilayer wiring structure 111 is formed at the upperportion of the circuit formation member 402. The multilayer wiringstructure 111 has a first wiring layer 128 and a second wiring layer129. The structure and production method of the multilayer wiringstructure 111 are similar to those of the multilayer wiring structure107 of the PD formation member 401. Next, after forming the secondwiring layer 129, a diffusion prevention film 131 covering the secondwiring layer 129 is formed. The diffusion prevention film 131 is formedof, for example, silicon nitride or silicon carbide. The diffusionprevention film 131 is for suppressing diffusion to the high-meltingmetal PD formation member 401. Thereafter, portions of the diffusionprevention film 131 are removed so that some wires of the second wiringlayer 129 constituting the connection portion 311 are exposed. Here, thediffusion prevention film may be removed by etching or CMP technology.Here, the circuit formation member 402 becomes the second substrate 108.A principal surface 109 of the second substrate 108 is determined asshown in FIG. 4B.

Next, as shown in FIG. 5A, the principal surfaces (105, 109) of the PDformation member 401 and the circuit formation member 402 are disposedso as to face each other, and are joined to each other by, for example,a micro-bump.

Finally, as shown in FIG. 5B, an undesired portion 404 and theinsulating layer 403 of the PD formation member 401 are removed by, forexample, CMP or etching, so that the PD formation member 401 is madethinner, to form the first substrate 104. Thereafter, an antireflectionfilm 118, formed of silicon carbide, is formed at the upper portion of aback surface 106 of the first substrate 104. After forming theantireflection film 118, a tungsten film is formed at the upper portionof the antireflection film 118 for patterning, thereby forming alight-shielding film 119. Thereafter, a planarizing layer and a colorfilter 120 are formed, and a microlens 121 is formed. Such a productionmethod makes it possible to produce the solid-state image pickupapparatus 400 shown in FIG. 3.

Here, according to the structure of the embodiment, after forming theinterlayer insulating film of the multilayer wiring structure 107, it ispossible to perform heat treatment at a high-temperature or for a longtime for improving characteristics such as recovery from defects of thephotoelectric conversion element. If the first substrate is providedwith a high-melting-metal compound layer, a high-melting metalsemiconductor compound layer is formed before forming the interlayerinsulating film. After forming the interlayer insulating film, itbecomes difficult to perform heat treatment at a high temperature or fora long time due to problems such as diffusion of the high-melting metal.Therefore, according to the structure of the embodiment, since heattreatment for recovering from defects of the photoelectric conversionelement may be optionally performed, it is possible to suppress areduction in the characteristics of the photoelectric conversionelement.

In a desirable form, for increasing connection resistance of a contactprovided at an FD region, it is desirable to perform ion implantationand heat treatment on the semiconductor region that is connected to aplug. However, as mentioned above, if the first substrate is providedwith a high-melting-metal compound layer, it becomes difficult toperform heat treatment in a contact formation step that is carried outafter forming the interlayer insulating film. Therefore, according tothe structure of the embodiment, it is possible to perform sufficientheat treatment in the step of forming the contact at the FD region wherethe high-melting-metal compound layer is not provided while thehigh-melting-metal compound layer is provided at the peripheral circuitportion. Therefore, it is possible to properly connect the contact atthe FD region while reducing contamination of the high-melting metal atthe FD region.

As discussed above, according to the solid-state image pickup apparatusof the embodiment, it is possible to further suppress generation of darkcurrent at the photoelectric conversion element while increasing thespeed of operation of the transistor at the peripheral circuit portionand increasing the speed of a signal readout operation.

Fourth Embodiment

A solid-state image pickup apparatus according to this embodiment willbe described with reference to FIG. 6. The structure of the solid-stateimage pickup apparatus according to this embodiment corresponds to thestructure of the solid-state image pickup apparatus according to thesecond embodiment, and differs therefrom in that it includes a diffusionprevention film. The structure shown in FIG. 6 will hereunder bedescribed. The structural features that are equivalent to those of thesecond embodiment will not be described.

In a solid-state image pickup apparatus 500 shown in FIG. 6, a diffusionprevention film 231, which prevents diffusion of a high-melting metal,is disposed between a first chip 201 and a second chip 202. By providingsuch a diffusion prevention film 231, it is possible to further suppressmixing of a high-melting metal of a high-melting-metal compound layerdisposed at the second chip into a semiconductor region constituting anFD region and a photoelectric conversion element of the first chip.Therefore, it is possible to suppress production of a white defect (ofan image) or a dark current. The diffusion prevention film 231 is a filmformed of, for example, silicon nitride or silicon carbide.

Next, a method of producing the solid-state image pickup apparatus 500shown in FIG. 6 will be described with reference to FIGS. 7A to 9.First, in FIG. 7A, a photo-diode formation substrate (hereunder referredto as “PD formation member”) 501, which becomes a first substrate 204shown in FIG. 6, and a circuit formation member 502, which becomes asecond substrate 208 shown in FIG. 6, are provided. The PD formationmember 501 includes a p-type semiconductor region 216 and an insulatinglayer 503. The PD formation member 501 uses an SOI substrate, and thep-type semiconductor region 216 may be formed by epitaxial growth or ionimplantation. The circuit formation member 502 uses an SOI substrate andincludes an insulating layer 234.

Next, in the PD formation member 501 shown in FIG. 7B, elements such asa gate electrode 214 of a transfer transistor, a charge storage region212, and a well 215 are formed. A multilayer wiring structure 207 isformed on the upper portion of the PD formation member 501. Themultilayer wiring structure 207 includes a first wiring layer 222 and asecond wiring layer 223. The structure and production method of themultilayer wiring structure 207 are similar to those of the thirdembodiment, so that they will not be described. Next, an interlayerinsulating film covering the second wiring layer 223 is formed, andportions of the interlayer insulating film are removed so that wires ofthe second wiring layer 223 are exposed. The second wiring layer 223constitutes a connection portion 311. Then, a diffusion prevention film231 covering the second wiring layer 223 and formed of, for example,silicon nitride or silicon carbide is formed. The interlayer insulatingfilm covering the second wiring layer 233 may be disposed between thesecond wiring layer 223 and the diffusion prevention film 231.

In the circuit formation member 502 shown in FIG. 7B, a transistorincluding an amplification transistor and a well 224 are formed. Then, ahigh-melting metal is deposited on predetermined positions, such as asource region, a drain region, and a gate electrode of the transistor,and heat treatment is performed, thereby forming a high-melting-metalcompound layer 230. Thereafter, a multilayer wiring structure 211 isformed on the upper portion of the circuit formation member 502. Themultilayer wiring structure 211 has a first wiring layer 228. Thestructure and production method of the first wiring layer 228 aresimilar to those of the third embodiment.

Next, in FIG. 8A, an adhesive layer 506 and a supporting base 507 areformed at the upper portion of the first wiring layer 228 at the circuitformation member 502. Then, an undesired portion 504 of the circuitformation member 502 is removed by abrasion or etching, and the secondsubstrate 208 is formed.

In FIG. 8B, a principal surface 205 of the PD formation member 501,which becomes the first substrate 204 shown in FIG. 6, and a backsurface 210 of the second substrate 208 are placed upon each other so asto face each other, and are joined together by, for example, amicro-bump. Then, the first adhesive layer 506 and the first supportingbase 507 are removed. Thereafter, an interlayer insulating film isformed on the upper portion of the first wiring layer 228 at the secondsubstrate 208, and a through electrode 235 for electrical connectionwith the first substrate 204 is formed. The through electrode 235 may beproduced by a general semiconductor process. Then, the through electrode235 is covered, and the second wiring layer 229 is formed.

Next, as shown in FIG. 9, an adhesive layer 232 and a supporting base233 are provided on the upper portion of the second wiring layer 229 atthe second substrate 208. Then, an undesired portion 505 at the PDformation member 501 is removed by, for example, CMP or etching, and thefirst substrate 204 is formed. Thereafter, an antireflection film 218,formed of, for example, silicon nitride, is formed at the upper portionof a back surface 206 of the first substrate 204. Then, alight-shielding film 219, formed of, for example, tungsten, is formed atthe upper portion of the antireflection film 218. Further, a planarizinglayer and a color filter 120 are formed at the upper portion of thelight-shielding film 219, and a microlens 121 is formed. Such aproduction method makes it possible to produce the solid-state imagepickup apparatus 500 shown in FIG. 6.

Even in the structure according to the embodiment, since heat treatmentof a contact or a photoelectric conversion element can be optionallyperformed, it is possible to suppress a reduction in the characteristicsof the photoelectric conversion element and an increase in theconnection resistance of the contact.

As discussed above, according to the solid-state image pickup apparatusof the embodiment, it is possible to further suppress generation of darkcurrent at the photoelectric conversion element while increasing thespeed of operation of the transistor at the peripheral circuit portionand increasing the speed of a signal readout operation.

Fifth Embodiment

A solid-state image pickup apparatus according to this embodiment willbe described with reference to FIGS. 10A to 10C. The structures ofsolid-state image pickup apparatuses 600, 610, and 620 according to theembodiment shown in FIGS. 10A to 10C correspond to the structure of thesolid-state image pickup apparatus 400 according to the thirdembodiment, with the disposition of the diffusion prevention film 131being modified. The structural features that are equivalent to those ofthe third embodiment will not be described below.

In the solid-state image pickup apparatus 600 shown in FIG. 10A, thediffusion prevention film 131 is disposed between a first substrate 104and a second substrate 108, and serves as an interlayer insulating filmincluded in a multilayer wiring structure 107 disposed at the upperportion of the first substrate 104. By virtue of such a structure, it ispossible to omit the step of forming an interlayer insulating film, andto make the solid-state image pickup apparatus thin. In addition, sincethe solid-state image pickup apparatus 600 is a backside-illuminationsolid-state image pickup apparatus, even if the diffusion preventionfilm 131, formed of, for example, silicon nitride, is provided on theentire top surface of a photoelectric conversion element, for example,reflection resulting from the difference between the refractive indicesof the diffusion prevention film 131 and a silicon oxide film, which isa general interlayer insulating film, does not occur. Therefore, it ispossible to suppress diffusion of a high-melting metal from the secondsubstrate 108 while suppressing a reduction in the opticalcharacteristics. The structure in which the diffusion prevention film131 serves as an interlayer insulating film is not limited to thestructure shown in FIG. 10A. For example, an interlayer insulating filmin a multilayer wiring structure 111 disposed at the upper portion ofthe second substrate 108 may be used.

Next, in the solid-state image pickup apparatus 610 shown in FIG. 10B,the diffusion prevention film 131 is disposed between a first substrate104 and a second substrate 108. In addition, the diffusion preventionfilm 131 is formed so as to contact a high-melting-metal compound layer130 on a source region and drain region 125 and a gate electrode 126 atthe second substrate 108. By virtue of such a structure, it is possibleto use the diffusion prevention film 131 as an etching stop layer whenforming a contact hole of the second substrate 108.

Next, in the solid-state image pickup apparatus 620 shown in FIG. 10C,the diffusion prevention film 131 is disposed between a first substrate104 and a second substrate 108, and contacts the upper portion of afirst wiring layer 228 at the second substrate 108. The first wiringlayer 228 is formed of copper wires. The diffusion prevention film 131also functions as a diffusion prevention film, which prevents diffusionof copper. By virtue of such a structure, it is possible to omit thestep of forming the diffusion prevention film, which prevents diffusionof copper, and to make the solid-state image pickup apparatus thin. Thestructure in which the diffusion prevention film 131 serves as adiffusion prevention film, which prevents diffusion of copper, is notlimited to the structure shown in FIG. 10C. For example, a multilayerwiring structure 107 disposed on the upper portion of the firstsubstrate 104 may be formed of copper wires, and the diffusionprevention film 131 may be formed for each wiring layer.

Sixth Embodiment

A solid-state image pickup apparatus according to this embodiment willbe described with reference to FIGS. 11A to 11C. The structures ofsolid-state image pickup apparatuses 700, 710, and 720 according to theembodiment shown in FIGS. 11A to 11C correspond to the structure of thesolid-state image pickup apparatus 500 according to the fourthembodiment, with the disposition of the diffusion prevention film 231being modified. The structural features that are equivalent to those ofthe fourth embodiment will not be described below.

In the solid-state image pickup apparatus 700 shown in FIG. 11A, thediffusion prevention film 231 is disposed between a first substrate 204and a second substrate 208, and serves as an interlayer insulating filmincluded in a multilayer wiring structure 207 disposed at the upperportion of the first substrate 104. By virtue of such a structure, it ispossible to omit the step of forming an interlayer insulating film, andto make the solid-state image pickup apparatus thin. In addition, thesolid-state image pickup apparatus 700 is a backside-illuminationsolid-state image pickup apparatus. Therefore, even if the diffusionprevention film 231, formed of, for example, silicon nitride, isprovided on the entire top surface of a photoelectric conversionelement, it is not necessary to consider reflection of incident lightresulting from the difference between the refractive indices of thediffusion prevention film 231 and a silicon oxide film, which is ageneral interlayer insulating film. Therefore, it is possible tosuppress diffusion of a high-melting metal from the second substrate208.

In the solid-state image pickup apparatus 710 shown in FIG. 11B, thediffusion prevention film 231 is disposed between a first substrate 204and a second substrate 208, and contacts the upper portion of a firstwiring layer 222 at the first substrate 208. The first wiring layer 222is formed of copper wires. The diffusion prevention film 231 alsofunctions as a diffusion prevention film, which prevents diffusion ofcopper. By virtue of such a structure, it is possible to omit the stepof forming the diffusion prevention film, which prevents diffusion ofcopper, and to make the solid-state image pickup apparatus thin. Thestructure in which the diffusion prevention film 231 serves as adiffusion prevention film, which prevents diffusion of copper, is notlimited to the structure shown in FIG. 11B. For example, as shown inFIG. 11C, of portions of a multilayer wiring structure 207 disposed atthe upper portion of the first substrate 204, the second wiring layer223 may be formed of copper wires, and the diffusion prevention film 231may be disposed on the upper portion of the second wiring layer 223.Here, the diffusion prevention film 231 may be disposed at the upperportion of the first wiring layer 222. In order to reduce the capacitybetween the wiring layers, it is possible to perform patterning of adiffusion prevention film, which prevents diffusion of copper, inaccordance with the forms of the wires at the upper portion of the firstwiring layer 222, and remove a portion thereof. As shown in FIG. 11C, amultilayer wiring structure 211, disposed on the upper portion of asecond substrate 208, may be formed of copper wires, and may include acopper diffusion prevention film 901.

Seventh Embodiment

In the embodiment, a case in which a photoelectric conversion apparatusaccording to the present invention is applied as an image pickupapparatus to an image pickup system is described in detail. The imagepickup system may be, for example, a digital still camera or a digitalcamcorder. A block diagram of a case in which a photoelectric conversionapparatus is applied to a digital still camera, which is an example ofthe image pickup system, is shown in FIG. 13.

In FIG. 13, reference numeral 1 denotes a barrier for protecting a lens,reference numeral 2 denotes a lens where an optical image of an objectis formed at an image pickup apparatus 4, and reference numeral 3denotes an aperture stop for varying the quantity of light transmittedthrough the lens 2. Reference numeral 4 denotes the image pickupapparatus, which is the solid-state image pickup apparatus described inany of the aforementioned embodiments. The image pickup apparatus 4converts the optical image formed by the lens 2 as image data. Here, anAD converter is disposed at the image pickup apparatus 4. Morespecifically, the AD converter is formed at the second chip. Referencenumeral 7 denotes a signal processing section that performs variouscorrections and data compression on image pickup data output from theimage pickup apparatus 4. In addition, in FIG. 13, reference numeral 8denotes a timing generating section that outputs various timing signalsto the image pickup apparatus 4 and the signal processing section 7, andreference numeral 9 denotes an overall control/operation section thatperforms various operations and that controls the entire digital stillcamera. Reference numeral 10 denotes a memory section that temporarilystores the image data, reference numeral 11 denotes an interface sectionfor performing a recording operation or a readout operation on arecording medium, and reference numeral 12 denotes the recording mediumthat is removable, such as a semiconductor memory for recording orreading out the image pickup data. In addition, reference numeral 13denotes an interface section for performing communication with, forexample, an external computer. Here, for example, a timing signal may beinput from outside the image pickup system, and the image pickup systemmay include at least the image pickup apparatus 4 and the signalprocessing section 7 that processes an image pickup signal output fromthe image pickup apparatus. Although, in the embodiment, the case inwhich the AD converter is provided at the image pickup apparatus 4 isused, the image pickup apparatus and the AD converter may be provided atdifferent chips. In addition, the signal processing section 7, etc. maybe provided at the image pickup apparatus 4. Since a high-melting-metalcompound layer is formed at the second chip of the image pickupapparatus 4, signal processing, etc. can be performed at a high speed.Accordingly, the photoelectric conversion apparatus according to thepresent invention is applicable to an image pickup system. By applyingthe photoelectric conversion apparatus according to the presentinvention to an image pickup apparatus, high-speed shooting can beperformed.

As mentioned above, the solid-state image pickup apparatus according tothe present invention makes it possible to provide a solid-state imagepickup apparatus that can perform high-speed operations. Further, thediffusion prevention film makes it possible to reduce dark current, andto suppress the production of a white defect in an image. Theembodiments are not limited to the described structures, and theembodiments may be combined as required. For example, the solid-stateimage pickup apparatus may include a plurality of diffusion preventionfilms, which prevents diffusion of a high-melting metal.

The high-melting-metal compound layer may be formed at a portion wherean electrical potential is applied to a semiconductor region, such as awell contact, in addition to the source region, the drain region, andthe gate electrode of a transistor.

According to the present invention, it is possible to provided, by usinga simple structure, a solid-state image pickup apparatus in which ahigh-melting-metal compound layer is disposed at a peripheral circuitportion while a reduction in the characteristics of a photoelectricconversion element is suppressed.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a solid-state image pickupapparatus used in an image pickup system, such as a digital still cameraor a digital camcorder.

REFERENCE SIGNS LIST

-   -   101 first chip    -   102 second chip    -   103 bonding surface    -   104 first substrate    -   107 multilayer wiring structure    -   108 second substrate    -   111 multilayer wiring structure    -   112 photoelectric conversion element    -   124 well    -   125 source/drain region    -   126 gate electrode of amplification transistor    -   130 high-melting-metal compound layer

What is claimed is:
 1. An apparatus in which a first substrate and asecond substrate are placed upon each other, the first substrate beingwhere a photoelectric conversion element and a gate electrode of atransfer transistor for transferring an electric charge from thephotoelectric conversion element are disposed, the second substratebeing where a peripheral circuit portion for reading out a signal basedon the electric charge generated at the photoelectric conversion elementis disposed, wherein the second substrate is provided with ahigh-melting-metal compound layer, and wherein the first substrate isnot provided with a high-melting-metal compound layer.